A proposed motor vehicle sets permission and prohibition for an idle stop of an engine, based on the outside air temperature and the air blow temperature at an air outlet for heating located in a passenger compartment of the vehicle (see, for example, Japanese Patent Laid-Open Gazette No. 2001-341515). This proposed motor vehicle prohibits the idle stop of the engine when the outside air temperature is lower than a preset first temperature or when the air blow temperature at the air outlet is not lower than a preset second temperature. Such prohibition ensures exertion of the sufficient heating performances of an air conditioning system mounted on the motor vehicle.